In metalworking, it has long been customary to use coated tools since they are superior to uncoated tools in many of their properties: higher operating temperatures, higher cutting speeds, longer tool-life, edge stability, corrosion resistance, etc. However, films optimized for wear protection and hardness are also used on other components which are exposed to comparable conditions in use and consequently require the same kind of properties; bearing parts and components for the automobile industry such as coated pistons, injection nozzles, etc., are examples of these.
Another aspect of coating is the problem of stripping, in particular for parts whose coating is flawed or—in the case of tools—which have to be stripped, reworked and coated once more.
The manifold service requirements result in a whole series of specialized coating and coating systems which in turn involve various stripping requirements. Stripping should be economical (rapid, only simple apparatus, low-priced consumer materials, usable for as many coatings as possible), safe (as few dangerous substances as possible), environmentally friendly and, not least, the coated tool or component should not be damaged by the stripping procedure.